Kind: captions
Language: en
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meet paleos seismologist Bryant
Atwater he and I are paddling up the
Copalis a coastal river that rises and
falls with Pacific Ocean Tides we're
here at low
tide but at high tide the river can rise
enough to overflow its banks flooding
the surrounding marshes with
saltwater but it wasn't always that way
once this was a lush Coastal rainall
Forest Now All That Remains are massive
Roots sticking out of the eroded river
bank and the trunks of long dead cedar
trees a ghost Forest Brian has brought
me here to show me evidence of one of
the worst earthquakes that hit North
America since human beings arrived here
slicing into the bank reveals three
layers they tell a story of change over
time the lowest once supported a healthy
rainforest so this is almost like a
garden soil right but it's got tree
roots in it it's a forest floor
soil just above is a layer of sand
entirely out of place its sharp
definition tells at water that whatever
put it here came fast and furious how do
we do this combination how do we go from
forest floor to some kind of Muddy
flat and have a sand layer brought in
first the answer lies about 80 M away at
the bottom of the Pacific Ocean it's
called the Cascadia subduction zone a
700m long crack in the crust of the
planet it's where a Pacific ocean plate
is trying to slide under the North
American
Plate but the plates are stuck they go
closer and closer like that and the
overriding plate gets shortened and
bulges up
the old growth forest that once stood
around the copellis river sat on that
bulge but then the plates Broke Free
along the
fault causing a violent
earthquake dropping 600 mies of
Coastline as much as 5 ft and into the
tidal Zone that same tectonic rupture
also drove the edge of the continental
plate
upward and triggered a series of huge
waves a tsunami
what the forest sees is a rush of
saltwater and sand inundating the
land the final Blow from a massive fault
rupture that turned an old growth
rainforest into
this we now know that this cataclysmic
onew punch took place in the year
1700 today everyone wants to know will
it happen again
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